Electrolytic cell cover



Nov. 1, 1960 v. DE NORA 2,958,635

ELECTROLYTIC CELL COVER Filed Dec. 24, 1957 2 Sheets-Sheet l ATTORNEYS Nov. 1, 1960 V v. DE NORA 2,958,635

' ELECTROLYTIC CELL COVER Filed Dec. 24, 1957 2 Sheets-Sheet 2 INVENTOR United States Patent Ofiicc 2,958,635 Patented Nov. 1, .1960

ELECTROLYTIC CELL COVER Vittorio De Nora, Milan, Italy, assignor to Gronzio De Nora Impianti Elettrochimici, Milan, Italy, a corporation of Italy Filed Dec. 24, 1957, Ser. No. 704,982

15 Claims. (Cl. 204-125) This invention relates to electrolytic cells for the electrolysis of electrolytic solution or molten salts. The invention more particularly relates to a new type of cover for such a cell and to a new method for supporting the anode of the cells. The invention will be described as applied to a horizontal mercury cell although it will be obvious that the principles of the invention can be applied to all types of electrolysis cells either of the mercury or diaphragm type for the electrolysis of aqueous electrolytes or molten salts in which anodes may be supported on a rigid frame Work resting on the cell walls or outside cell structure and a flexible cover provided to close the cell between the cell walls and the anode support frame.

Examples of cells of the type intended to be included in this invention are described in United States Patent 2,544,138, granted March 6, 1951, and in Industrial and Engineering Chemistry, 1953 (vol. 45, No. 6), pages 1162-1172. The use of the cell covers such as herein described on other cells of similar construction are also included within the scope of this invention. These cells generally designated as horizontal mercury cells consist of an enclosed, elongated trough sloping slightly towards one end. -The cathode is a flowing layer of mercury which is introduced at the higher end of the cell and flows along the bottom of the cell toward the lower end. The anodes are generally composed of flat rectangular plates of graphite suspended from graphite or copper rods in such a manner that their flat surface is spaced a short distance above the flowing mercury cathode. The body and sides of the trough are generally steel with a corrosion resistant lining of hard rubber, concrete, stone or other non-conducting material. The lining may comprise a concrete which is further coated with resin, or has natural stone set in the concrete lining.

In the operation of this type of cell the electrolyte, which may be brine or an aqueous solution of any electrolyte compound which upon electrolytic decomposition will give the products desired, is introduced at the upper end of the cell and flows toward the lower end of the cell. For example, a solution of sodium chloride may be electrolyzed in such a cell. Electric current passes through the solution between the anodes and the mercury cathode. When sodium chloride is the electrolyte, chlorine is formed at the anodes and passes to the top of the cell and out through an opening in the cell cover which is provided for this purpose. Sodium is formed at the cathode and amalgamates with the mercury cathode. The sodium amalgam is withdrawn at the lower end of the cell, cycled to a decomposer packed with graphite Where it is contacted with water to form sodium hydroxide, hydrogen and mercury. The mercury is recycled to the cell for reuse as the cathode. It will be understood that other electrolytes, such as potassium chloride, barium chloride, lithium chloride, sodium sulfate and the like may also be electrolyzed in such a cell.

In cells of this type the distance between the graphite anodes and the mercury cathode is very important. This distance should be as small as possible to reduce consumption of energy but if this distance is too small, secondary reactions take place, particularly the direct attack of sodium amalgam by chlorine bubbles. The graphite anodes are generally suspended by attaching them on graphite posts attached to connectors extending through the cover of the cell and the connectors are connected to bus bars outside the cell cover. Each graphite anode is thus fastened by connections to the cell cover in such a Way that it is at a proper distance from. the cathode when the cover is placed on the cell. The cell cover is usually a steel plate covered with rubber and sufiiciently strong to support the anodes and the electrical connections thereto. Stoneware or hard rubber covers are sometimes used but these must be sufiiciently thick and strong to support the anodes therefrom. The distance between the anodes and cathode is determined by the way in which the cover fits on the cell and the adjustment of the anodes in the cell cover.

In operation the graphite anodes are consumed thereby increasing the distance between the anodes and cathode and resulting in reduced current efliciency. To maintain the proper distance or spacing between anodes and cathodes it is necessary in this type of prior art apparatus to adjust each anode individually. Another disadvantage is that lifting of the cover of the cell for inspection or repair moves all the anodes and disturbs their adjustment. In some cases, the position of the individual anodes can be varied with respect to the cell cover, but this is often a complicated operation or requires a complicated device.

Explosions resulting from a combination of electrolytic product gases occasionally occur in cells of this type as Well as in electrolytic cells of other types with consequent damage to the rigid cover for the cell and complete disarrangement of the anodes as well as possible danger to operating personnel in the cell room.

Attempts have been made to solve the problem of anode to cathode spacing by providing strips or shims between the cover and the sides of the cell. These strips or shims were removed after a certain amount of consumption of the anodes had taken place to lower the cell cover and thereby reduce the spacing between the anodes and the cathode. However, accurate adjustment by such a method was not possible. In the most commonly used prior art construction the anodes are individually attached to the cover of the cell which rests on the side walls of the cell trough and are individually adjustable thereon.

One of the objects of this invention is to provide a rigid frame work for supporting the anodes of an electrolytic cell and permitting adjustment of the spacing between the anodes and the cathode, independent of the cell cover.

Another object is to provide a flexible cell cover of rubber, plastic, or other material whereby the cover may be lifted for inspection of the interior of the cell without disturbing the anode adjustment and whereby the anodes may be adjusted if desired, without removing the cell cover or disturbing the seal between the cell cover and the edges of the cell.

Another object of this invention is to provide a supporting frame for the anodes of an electrolytic cell which will permit easy adjustment of the distance between the anodes and the cathodes.

Another object of this invention is to provide a supporting frame for the anodes of an electrolytic cell which will allow simultaneous adjustment of all anode electrodes, or of all anodes of a large section of the cell.

A further object of this invention is to providea flex ible cover for an electrolytic cell. independent ofsaid anode supporting frame whereby adjustment of the dislance between anodes and cathodes may be made without removing the cover of the cell.

Another object of this invention is to provide a cover for an electrolytic cell whereby the edges of the cover may be lifted without movement of the anodes or anode supporting frame or disturbance of the arrangement of the anodes.

A further object of this invention is to provide a cover for an electrolytic cell which will allow dissipation of explosive forces within the cell without serious damage to the cover and anodes of the cell.

Another object of the invention is to provide support for the anodes of an electrolytic cell of the type herein described which is supported from the cell trough or outside of the cell trough independently of the cell cover and to provide a flexible stretchable cell cover to be used with such support.

Various-other objects and-advantages of the invention will become apparent as this description proceeds.

These objects are accomplished and the disadvantages of the prior art structures overcome by the use of my invention which comprises supporting the anodes from a rigid spider shaped metal frame structure supported on the cell trough or on a support structure outside the trough, and providing a flexible stretchable cell cover to close the space between the anode frames and the cell trough. The metal frame work consists of support members extending transversely of the cell and provided with means at their outer ends for fitting the frame upon vertical posts which rest upon or are attached to the trough of the electrolytic cell. The anodes are attached to and suspended from these rigid transverse frame members and the position of each anode can be adjusted independently. The height of the metal frame above the cell may be adjusted by suitable adjusting nuts located on said posts on which the transverse members of the frame are attached. By adjustment of the height of the frame the distance between the anodes and the inside bottom or cathode of the cell is also adjusted,

The top of the cell is closed by providing a cover of flexible material, such as rubber, polyvinyl chloride or other sheet plastic or the like, which is fastened to the sides of the cell either by bolting or by a suitable clamping means. Holes are provided in the flexible cover through which the anode connections protrude and means are provided for sealing between the cover and the anode connections. By this construction the height or distance of all the anodes from the cathode may be adjusted simultaneously by adjusting the nuts which determine the height of the supporting frame above the cell trough. The supporting frame has suflicient flexibility to allow lowering of one section of the frame while the rest of the adjusting screws have not yet been adjusted. The lowering of the frame is usually less than ,6 at a given adjustment. Because of the flexibility of the rubber or plastic cover, it has sufficient give to allow adjustment of the anodes without disturbing the cover or destroying the seal between the cover and the cell trough or between the cover and the anodes.

Another advantage to this type of cover is the fact that the edges of the rubber cover may be lifted for inspection of the inside of the cell without disturbing the arrangement of the anodes. In addition, serious damage to the cell is prevented from the accumulation of explosive mixtures of gases within the cell. In the event of explosion the flexible cover merely expands in much the same manner as a balloon under the pressure of these gases, and if expansion is continued, it merely results in local rupture of a small area of the cover thereby allowing the excess gases to escape harmlessly without any disturbance of the remainder of the structure of the cell or the dangers accompanying an explosion. Repair or replacement of the cover is readily accomplished by replacing the torn cover section or by merely sealing, patching or vulcanizing the torn section,

The invention may be more readily understood by referring to the drawings illustrating a preferred embodiment of the invention.

In the drawings which illustrate a preferred embodiment of the invention- Fig. 1 represents a perspective elevation with parts broken away of an electrolytic cell embodying this invention in combination with the decomposer.

Fig. la is an enlarged detail perspective of one end of the anode electrical connections.

Fig. 1b is an enlarged detail perspective of the other end of the anode electrical connections as viewed from the line 1b1b of Fig. 1. a a

Fig. 2 is a partial cross-sectional side view substantially along the line 2-2 of Fig. 1 showing the anode bus bar connection and showing how the cell cover is divided into sections.

Fig. 3 is a cross-sectional view of the cell takenalong the lines 3--3 of Fig. 1 with parts broken away.

Fig. 3a illustrates an alternative method of supporting the cell spider by supports outside the cell trough.

Figs. 4 and 5 illustrate modifications of the means for attaching the cell cover to the cell base. i

Referring to the drawings, the metallic base 1 of the cell is preferably formed from steel I-beam sides 1A and a flat steel bottom 1B. This body is lined with concrete 6 and the sides and bottom of the cell are lined with layers of a natural stone material 5 or other resistant material, such as a coating of resin. At suitable intervals the bottom of the cell is crossed by steel I-beam sections 9 which are connected to the bottom 1B and which act as electrical connectors between the mercury flowing along the cell floor and the negative bus bar 12. The anodes comprise flat horizontal graphite plates 8 attached to vertical cylindrical graphite anode rods 27, which in turn are provided with metallic conductor bolts 30 for attachment to the positive bus bar 11 and for attachment to the anode supporting frame structure.

The anodes are suspended and supported from a metal frame spider 15 which consists of transverse bars 20 secured to longitudinal I-beams 21. The transverse bars 20 are adjustably supported on posts 19 which rest upon or are secured to the sides 1A of the cell trough or rest upon rigid supports outside the cell trough. Adjusting means such as screw threaded nuts 22 are provided on the posts 19 so that the height of the spider 15, and of the anodes supported therefrom, can be adjusted relative to the cell trough. Suitable means, such as an eye hook 32 is provided on the frame 15 for lifting the whole frame off the cell, with the anodes suspended therefi'om', when desired.

Anode support bars 40' are attached to the I-beams 21 at spaced intervals as indicated in Fig. 1 and the anodes 8 are suspended from the bars 40 by connector bolts 30 and nuts 31. Bars 40 are connected to the I-bearns 21'of the frame 15 by welding or the like.

As shown in Fig. 3a, frame spider 15 may be supported by posts 19a resting upon a rigid support outside the cell trough rather than on the sides of the cell trough. It is mainly necessary that frame 15 be supported in a fixed position with respect to the cell trough, and be adjustable relative thereto.

As illustrated in Fig. 1 the cover of the cell is divided into three sections A, B and C by transverse dividing bars A and B extending across the top of the cell trough and the anodes supporting frames or spiders 15 are like; wise divided into three separate sections so that each section may be lifted or adjusted separate from the other section. j

A flexible cover 17 made of sheet rubber or other sheet plastic material through which the anode connections 30 protrude, closes the'top of the cell and is fastened to the sides of the cell and the transversed dividing bars A and B by means of bolted strips 24. Other suitable clamping means can be provided such as pressure feet 24A con-,

nected to .the frames 15 by bars 24B as shown in Fig. 4 or by pressure members 24D, pivoted on rods 24E connected to the irames 15 so as to press the flexible cover 17 against the sides 5 of the cellwhen the frames 15 are in position thereon as shown in Fig. 5. However, in this case the cell cover cannot be opened without moving the anode supporting frame. Suitable gaskets areprovided between anode rods 27 and connections 30 and the flexible cover- 17 to prevent escape of gases, and a chlorine outlet (not shown) is provided through the flexible cover 17 or through the side wall of the cell above the brine level.

Copper bus bars 12 provide electric connections for the cathode through the'bottom of plate 1B and through metallic I beams 9 which are connected to the base plate 1B and which are embedded in the lining of the cell and come into contact withthemercury flowing along the bottom of the cell (see Fig. 3). Electric connection is provided to the anodes 8 through bus bars 11 which are further attached to the electrical connections 16 which are attachedto the supporting posts 27'of each anode by spider connections 28 and nuts 29 on connector bolts 30 (see Figs. 1a and 1b).

With this arrangement, all of the anodes attached to the frame 15 may be simultaneously adjusted through the adjusting means 19 and 22 without disturbance of the flexible cover 17. It is thus possible to alwaysmaintain the proper distance for the most eflicient operation between the lower face of the anodes and the mercury cathode flowing along the bottom of the cell.

Fig. 2 shows ingreater detail the anode electrical connections 28 and bus bar '16 and how the flexible cover 17 for the entire cell is divided into three separate parts which are held together at their adjacent edges by strips 24 extending across the transverse bars A and B of the cell.

In the operation of a cell of the type shown in Fig. 1, mercury is introduced through conduit v into compartment 43 and passes under weir 43A into the cell compartment. A sodium chloride solution is introduced into the cell through inlet 41 at the end of the cell adjacent decomposer 2. The-mercury and brine flow towards the opposite end of the cell during which the brine is electrolyzed. Chlorine is withdrawn through the chlorine outlet and depleted brine is withdrawn at the lower end of the cell at outlet 42. Amalgam passes beneath Weir 45 into open compartment 46 and is withdrawn by conduit 33, passing through trap 34 to decomposer 2. In the decomposer, the sodium-mercury amalgam is reacted with Water to form sodium hydroxide, hydrogen and mercur-y. Water is fed to the decomposer through inlet 35. Hydrogen is withdrawn from outlet 36 and sodium hydroxide through outlet 37. Mercury flows out of the decomposer through conduit 38 and is recycled to the cell by pump 39 via conduit 10.

While I have set forth preferred embodiments of my invention to enable those skilled in the art to understand and practice my invention, it will be understood that the invention is not limited thereto and that various modifications may be made without departing from the spirit thereof and the scope of the claims. For example, this new type of cover may be used on other types of electrolytic cells in which it has previously been the practice to suspend the anodes from the cover of the cell. One example of such a cell is the vertical diaphragm cell described in the patent to Stuart 2,370,087. Other similar cells may also 'be suitable for the use of my new cover.

I claim:

1. An apparatus for conducting electrolysis of elec trolytic solutions which comprises an elongated inclined trough, upright members fastened to the sides of said trough, a metal frame comprising transverse and longitudinal members, said transverse members resting on said upright members and adjustable means to maintain said transverse members at a specified height above said the sides of said trough, openings in said cover through which said anodes protrude, a mercury cathode flowing along the bottom of said trough, and means for imposing an electrical current on said anodes and said cathode.

2. An apparatus for conducting electrolysis ofelectrolytic solutions which comprises an elongated inclined trough, upright members outside of'said trough, a metal frame comprising transverse and longitudinal members, said transversemembers being secured to said upright members, adjusting means on said upright members for controlling the height of said transverse members, anodes suspended from said transverse members of said frame, aflexible sheet cover attached to the sides of the cell and forming a gas tight enclosure for said cell, openings in said cover through which said anodes protrude, said openings forming a gas tight seal around said anodes, a mercury cathode flowing along the bottom of said cell, and electrical connections for said anodes and cathode.

3. An apparatus for conducting an electrolysis of electrolytic solutions comprising an elongated inclined trough, a flexible sheet cover attached to the sides of said trough, said cover containing openings for the passage of anodes therethrough, upright members resting on the sides of said trough, a metal frame superimposed above and spaced from said flexible sheet cover, said frame comprising transverse and longitudinal members, said transverse members being attached to said upright members, adjustable means for maintaining said frame at a specified height above said trough, anodes suspended from said frame and passing through said openings in said cover, a mercury cathode flowing along the bottom of said trough, and means to impose an electrical current on said anodes and said cathode.

4. In an amalgam electrolytic cell comprising an elongated inclined trough having the amalgam cathode flowing over the bottom of said trough, and anode electrodes suspended above the flowing amalgam, the improvement which comprises suspending said anodes from a metallic frame adjustably supported on vertical members resting on supports outside of said cell, and providing a flexible cover attached to the sides of said cell through which cover the anodes protrude.

5. In an amalgam electrolytic cell comprising an elongated inclined trough having the amalgam cathode flowing over the bottom of said trough, and graphite anode electrodes suspended above the flowing amalgam, the improvement which comprises suspending said anodes from a metallic frame comprising transverse and longitudinal members, supported on vertical members attached to the sides of said cell, and providing a flexible cover for said cell attached to the sides of said cell, said cover having openings through which the anodes protrude.

6. In an amalgam electrolytic cell comprising an elongated inclined trough having the amalgam cathode flowing over the bottom of said trough, and graphite anode electrodes suspended above the flowing amalgam, the improvement which comprises a metallic frame comprising transverse and longitudinal members supporting said anode electrodes, means to support said frame on vertical members attached to the sides of said cell from which said anodes are suspended and a flexible cover attached to the sides of said cell, said cover having openings through which the anodes protrude, said cover providing a gas tight enclosure for said cell.

7. In an amalgam electrolytic cell comprising an elongated inclined trough having the amalgam cathode flowing over the bottom of said trough, and graphite anode electrodes suspended above the flowing amalgam, the improvement which comprises a metallic frame comprising transverse and longitudinal members, means to support said frame on vertical members maintained in fixed relationship to the cell trough from which said anodes are suspended and a flexible cover attached to the sides ot? said cell, said cover having openings through which the anodes protrude, said cover providing a gas tight enclosure for said cell.

8. As an article of manufacture, a cover for an electrolytic cell which comprises a metal frame, vertical memlytic cell which comprises a rigid spider frame, vertical membersprojecting downwardly from said frame and resting on the sides of said cell, means for suspending anodes from said longitudinal members of said frame and flexible cover for closing the top of said cell, said cover being provided with holes through which the anode rods extend, and means for sealing said flexible cover to the sides of said cell.

10. As an article of manufacture, a cover for an amalgam electrolytic cell which comprises a frame of transverse and longitudinal members, vertical members projecting downwardly from said transverse member and resting on the sides of said cells, means for suspending anodes from said longitudinal members of said frame, a flexible cover for closing the top of said cell, said cover being provided with holes through which the anode rods extend, and means for sealing said flexible cover to the sides of said cell.

11. A method for maintaining the proper distance between the anodes and the cathode in an amalgam electrolytic cell, which comprises the steps of suspending the anodes fro-m a metal frame supported above and on the cell trough, providing means to adjust the height of said frame, and providing a cover for the cell extending from the walls thereof of a flexible material which will permit adjustment of the anodes without disturbance of the cover.

12, A method for maintaining the proper distance between the anodes and the cathode in an amalgam electrolytic cell which comprises the steps of suspending the anodes from a metal frame, providing means to adjust the height of said frame, and providing a cover for the cell extending from'the walls thereof and. interposed between said frame and said cell of a flexible material with openings for the passage of said anodes which will permit adjustment of the anodes without disturbance of the cover.

13. A method for maintaining the proper distance between the anodes and the cathode in an amalgam electrolytic cell, which comprises the steps of suspending the anodes from a metal frame, providing means to adjust the height of said frame above said cell and providing a cover for the cell of a flexible material attached to the sides of said cell and through which the anodes pass in gas tight relationship, said cover permitting adjustment of the anodes without disturbance of the cover. 7 q

14. The method of preventing damage to an electrolytic cell due to explosions which comprises suspending the anodes in said cell from an open metal spider and providing a flexible cover for said cell secured to the side walls thereof and sealed around said anode suspending means.

15. In a horizontal mercury cell, a trough, means to flow amalgam therethrough, an anode support over said trough comprising an anode supporting rigid spider, means to adjustably support said spider over said trough, means on said spider to support anodes in said trough and a flexible cover extending from the walls of said trough between said anodes and said spider and through which said anode support means extend in sealed relationship, and means to removably secure said cover to the walls of said trough.

References Cited in the file of this patent UNITED STATES PATENTS A Carter Feb. 27, 1951 

1. AN APPARATUS FOR CONDUCTING ELECTROLYSIS OF ELECTROLYTIC SOLUTION WHICH COMPRISES AN ELONGATED INCLINED TROUGH, UPRIGHT MEMBERS FASTENED TO THE SIDES OF SAID TROUGH, A METAL FRAME COMPRISING TRANSVERSE AND LONGITUDINAL MEMBERS, SAID TRANSVERSE MEMBERS RESTING ON SAID UPRIGHT MEMBERS AND ADJUSTABLE MEANS TO MAINTAIN SAID TRANSVERSE MEMBERS AT A SPECIFIED HEIGHT ABOVE SAID TROUGH, ANODES SUSPENDED FROM SAID TRANSVERSE MEMBERS OF SAID FRAME, A FLEXIBLE SHEET PLASTIC COVER ATTACHED TO THE SIDES OF SAID TROUGH, OPENINGS IN SAID COVER THROUGH WHICH SAID ANODES PROTRUDE, A MERCURY CATHODE FLOWING ALONG THE BOTTOM OF SAID TROUGH, AND MEANS FOR IMPOSING AN ELECTRICAL CURRENT ON SAID ANODES AND SAID CATHODE. 